J. ChiUPsychol. Piychial. Vol. 33, No. 8, pp. 1365-1372, 1992 Printed in Great Britain.

0021-9630/92 $5.00 + 0.00 Pergamon Press Ltd © 1992 Association for Child Psychology and Psychiatry

The Performance of Hyperactive and Control Preschoolers on a New Computerized Measure of Visual Vigilance: The Preschool Vigilance Task Gary W. Harper and Donald R. Ottinger Abstract—This study examines the ability of a new visual vigilance task, the Preschool Vigilance Task (PVT), to differentiate between hyperactive and control preschoolers. The PVT was designed to be an objective measure of attention specifically for use with the preschool-age population. Hyperactive and control preschoolers were tested on the PVT and the Continuous Performance Task (CPT). Results indicated that both were useful in differentiating between hyperactive and control preschoolers. Implications for the utility of the PVT and future research directions are discussed. Keywords: Attention, Attention Deficit Hyperactivity Disorder, Hyperactivity, Preschoolers, Vigilance

Introduction Research on Attention Deficit Hyperactivity Disorder (ADHD), or "hyperactivity",* within the school-age population has proliferated for several years (Barkley, 1982; Pelham, 1982), while investigation of this disorder within the preschool-age population has been sparse. Campbell's (1985) review of hyperactivity in preschoolers emphasizes the need for further investigation in the particular area of early detection and diagnosis of such children. Currently the child is often evaluated solely by a parent and perhaps a preschooler teacher and this evaluation may be greatly influenced by the amount of disruption and stress caused by the child. Since these evaluations are subject to bias and unknown bases of comparison, there exists a need for an objective performance measure to serve as an adjunetive aid in the evaluation of hyperactivity in the preschool population. Accepted manuscript received 10 February 1992

Department of Psychological Sciences, Purdue University, West Lafayette, IN 47907, U.S.A. Requests for reprints to: Donald R. Ottinger, Department of Psychological Sciences, Purdue University, West Lafayette, IN 47907, U.S.A. •The term "hyperactive" is used in this manuscript instead of ADHD because group membership was based solely on the Conners Parent and Teacher Rating Scales—Revised instead of a more comprehensive assessment which would be required to make a definitive diagnosis of an ADHD.

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Visual vigilance was selected as an objective measure of attentional ability that could be applied to the preschool-age population. Such tasks ascertain attentional ability via the recognition of a visual target stimulus which appears at aperiodic intervals during the viewing of additional competing stimuli. Kupietz and Richardson (1978) have demonstrated that vigilance performance is directly related to attentiveness in the classroom setting and is not merely a laboratory phenomenon. Several studies have clearly demonstrated that school-age hyperactive children's ability to sustain attention on visual vigilance tasks is deficient when compared to that of control children (e.g. O'Dougherty, Neuchterlein & Drew, 1984; Sykes, Douglas & Morgenstern, 1972, 1973; Zentall, 1986), but scant investigation of preschool children with hyperactivity has been conducted. The Continuous Performance Task (CPT: Rosvold, Mirsky, Sarason, Bransome & Beck, 1956) is the most commonly used method of assessing visual vigilance in children with suspected attentional deficits (Klee & Garfinkel, 1983; Rapport et al., 1986; Barkley, 1988). Although the CPT has been used frequently in the school-age population, its utility with preschoolers is questionable. Few studies have included preschool-age children in their sample (Sykes, Douglas, Weiss & Minde, 1971; Werry & Aman, 1975), with none being conducted specifically to assess attentional differences in this population. O'Dougherty and her colleagues (1984) have cautioned that the CPT may not be appropriate for the preschool-age population because of its reliance on knowledge of numbers or letters. Davies and Tune (1969) have even classified CPT-type tasks as "cognitive vigilance tasks", further recognizing that these tasks may require more than sustained attention. The literature on the use of non-CPT type vigilance tasks with preschool-age children is sparse. Herman, Kirchner, Streissguth and Little (1980) developed a visual vigilance task for this population which does not require previous knowledge of numbers or letters. Streissguth et al. (1984) used the same apparatus to detect reliable attentional differences in preschoolers. The apparatus used in the current study is a modification of that used by Herman et al. (1980) and Streissguth et al. (1984). The current study used both the CPT and the modified vigilance task [henceforth referred to as the Preschool Vigilance Task (PVT)] to assess attentional differences in hyperactive and control preschool-age children. The CPT was included to have a well studied task to compare with the new Preschool Vigilance Task (PVT). It was hypothesized that hyperactive preschoolers would display poorer performance than control preschoolers on both the CPT and PVT measures which assess accuracy of stimulus recognition (errors of commission and omission), and would perform just as well as control children on reaction time. In addition, a behavioral measure of inattention (head turns away from the task) was recorded during the task performance and was hypothesized to be related to performance on both the CPT and PVT. Method Subjects

Twenty hyperactive preschoolers (17 boys, 3 girls) and 20 control preschoolers (17 boys, 3 girls), matched on age and gender, participated in this investigation. Each group included 11 4-year-olds,

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five 5-year-olds and four 6-year-olds. The children were enrolled in kindergarten or preschool and were not currently taking any psychostimulant medication. Children were grouped according to scores on the Conners' Teacher Rating Scale—Revised (CTRS—R: Goyette, Conners & Ulrich, 1978) and the Conners' Parent Rating Scale—Revised (CPRS—R; Goyette et al., 1978). The criterion used to classify children as "hyperactive" was a mean score of at least 15 on the Hyperactivity Index of either the CPRS—R or the CTRS—R. This cutoff score on the Hyperactivity Index is generally accepted as an adequate means of establishing hyperactivity (Barkley, 1981) and has been used in numerous studies to date (e.g. Prinz, Tarnowski & Nay (1984), O'Dougherty et al. (1984), Ottinger, Halpin, Miller, Demian & Hannemann (1985)). Hyperactive children in the present study received a group mean score of 14 (S.D. = 6.9) on the CPRS—R and a group mean score of 15 (S.D. = 6.4) on the CTRS—R. Children in the control group were within the normal range on the Hyperactivity Index of both the CPRS—R and the CTRS—R (control group mean for CPRS—R = 5.0, S.D. = 3.9; control group mean for CTRS—R = 4.0, S.D. =4.4). Within the hyperactive group, five children met the criterion for "hyperactive" on both the CPRS—R and the CTRS—R, nine met the criterion on the CTRS—R only, and six met the criterion on the CPRS—R only. Measures

Preschool Vigilance Task (PVT). The apparatus used for this task was a modification of that used by Herman et al. (1980) and Streissguth et al. (1984). A picture of a tree appeared on a computer monitor and remained on the screen throughout the course of the task. One branch on the right-hand side of the tree was slightly extended away from the body of the tree and a bird appeared at intermittent intervals on this branch. The bird (henceforth referred to as the critical stimulus) was presented 25 times at intervals ranging from 10 to 60 sec. The interstimulus intervals were randomly chosen and each subject received the same sequence. Each stimulus appeared on the screen for .5 sec and the duration of the entire task was 14.5 min. The children were instructed to press a button only when the bird appeared on the tree branch. The computer controlled the presentation of the stimuli as well as recorded errors of commission (responses made when the critical stimulus was not displayed), errors of omission (nonresponse to the occurrence of the critical stimulus), and reaction time (speed of responses which occur after the occurrence of the critical stimulus). Continuous Performance Task (CPT). The CPT (Sykes et al, 1971) used in this study consisted of the computerized presentation of 12 letters (A, C, E, F, G, H, I, L, S, T, U, X) in a randomized serial order with the critical stimulus designated as the letter " X " . The order of the stimuli was the same across all subjects and conditions. Each stimulus was presented for .2 sec, with an interstimulus interval of 1.5 sec. The stimuli appeared on the computer screen at a height of 5 cm and a width of 3 cm. A total of 200 test stimuli, 30 of which were targets, were presented to each subject along with 20 practice stimuli. The entire task, therefore, took approximately 6 min and 20 sec to complete. The stimuli presentation and interstimulus interval, as well as a recording of errors of omission, errors of commission and reaction time were controlled by the computer. Behavioural measure of inattention. The amount of time that each child spent looking away from the computer monitor during task administration (time off task) was recorded as a measure of inattentiveness. Several studies have found higher rates of this type of behavior in hyperactive children during vigilance tasks as compared to normal children (Sykes et al., 1972; Higgins & Turnure, 1984). Experimenters sat in the back corner of the testing room and unobtrusively used an electronic stopwatch to record the amount of tim» that the child had his/her head turned more than 90° away from the monitor. This is the same criterion used by Werry and Quay (1969), Zentall (1980) and Zentall and Shaw (1980) in their studies demonstrating off-task differences between hyperactive and control school-age children. During 55% of the testing sessions (split evenly between groups), a second experimenter also recorded time off task so that interobserver reliability could be determined. Procedure

All subjects were tested on both the CPT and the PVT on two separate occasions, with at least one week elapsing between the time of the first and second visit. One half of the hyperactive group and one half of the control group received the CPT followed by the PVT during each of the two sessions

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(CPT/PVT) and one half of each group received the tasks in the opposite order (PVT/CPT). The order of task administration was kept constant across both testing sessions so that the test-retest reliability of this measure could be assessed. All children received standardized instructions for both tasks, and were pre-tested to ensure their understanding of the instructions.

Results Test-retest reliability

In order to determine the test-retest reliability of the various CPT and PVT measures, a series of Pearson product-moment correlations was computed (see Table 1). On the PVT, errors of omission demonstrated high reliability (;• = .80, /> = .0001) with errors of commission and reaction time failing to reach significance. On the CPT, errors of commission demonstrated high reliability (r= .75, p= .0001), errors of omission moderate reliability (r= .55, p= .0004) and reaction time failed to reach significance. Only those measures that achieved significant reliability were used in subsequent analyses. Table 1. Test-retest reliability of various CPT & PVT measures CPT

r

4}

Omission Commission Reaction Time

.55 .75 .16

.0004 .0001 .3461

PVT Omission Commission Reaction Time

.80 .06 .17

.0001 .7103 .2900

Note. Values given are Pearson productmoment correlations.

CPT and PVT main effects

Repeated measure analyses of variance were used to ascertain group differences on the reliable CPT and PVT measures.t There were significant main effects for the group (hyperactive vs control) on the CPT measures of errors of commission and errors of omission, and on the PVT measure of errors of omission (see Table 2). In order to determine the direction of effects, means and standard deviations were calculated using the subjects' scores on the respective measures collapsed across both testing sessions. Examination of group means revealed that hyperactive children made more errors of commission and omission than control children on the CPT, and more errors of omission on the PVT. 'Preliminary analyses revealed that subjects' performance did not differ significantly across age groups, therefore all analyses were conducted with subjects collapsed across all three age groups. A series of preliminary analyses were also conducted on the data to detect any significant effects due to task order (receiving CPT first vs PVT first) or to session order (performance during first session vs second session). None of these tests reached significance at the/?< .01 level (see Harper, 1989, for more details).

Vigilance in hyperactive preschoolers

Table 2. Main effects for group (hyperactives vs controls) CPT

Hyperactive Mean S.D.

Control Mean S.D.

F

p

Omission Commission TimeOffTask

10.65 11.52 9.47

.0024 .0017 .0040

18.53 20.00 33.15 sec

18.66 5.17 30.30 2.78 58.67 1.63 sec

6.73 2.51 2.19

PVT Omission TimeOffTask

49.58 17.03

.0000 .0002

22.90 112.94 sec

13.17 4.30 177.91 4.31 sec

3.81 6.94

Note. Omission = errors of omission. Commission = errors of commission, sec = seconds.

Behavioral Observation Effects

Interobserver reliability for the time off task variable was first determined using the mean ratio agreement, a procedure which was used to make reliability determinations of 90° head turn behavior by Werry and Quay (1969) and Zentall (1980). The method involves taking the data from two observers and dividing the snnaller number by the larger, converting it to a percentage, and then calculating the mean for the set of paired observations. A total of 14 mean ratio agreements were calculated to see if any particular task, testing session or group had low agreement. The range of mean ratio agreements across all combinations was 92.08-99.05%, thus indicating high interobserver reliability. Pearson product-moment correlations were computed between the reliable CPT and PVT measures and time off task. Errors of omission on both the CPT and PVT were significantly correlated with time off task (CPT: r= .33, jf7= .0486; PVT: r= .51, p = .0009), and errors of commission on the CPT were also significantly correlated with time off task {r= .78,p= .0001). Repeated measures analyses of variance revealed significant main effects for group (hyperactive vs control) on the time off task measure during both the CPT and PVT (see Table 2). Hyperactive children looked away from the monitor during 8.7 % of the CPT administration time (Af = 33.15 sec, SD = 58.67), with control children doing so only during 0.4 % of the time (jVf = 1.63 sec, 5D = 2.19). Hyperactive children reacted similarly on the PVT, spending 13.0% of the task time not attending {M= 112.94 seconds, 5Z)= 177.91), and control children did so during 0.5% of the time (Af=4.31 sec, 5Z) = 6.94). CPT and PVT discriminant analyses

In an attempt to determine the discriminative abilities of the CPT and PVT, linear discriminant analyses for two groups were conducted (Flury & Riedwl, 1988). These were only conducted on the errors of omission data since this is the only measure that demonstrated adequate reliability on both tasks. The analysis using only CPT errors of omission data for both sessions combined identified 83.3% of control children and 63.2% of hyperactive children, producing an overall correct classification rate of 73.0%. On the PVT, using only errors of omission data identified 90% of control and 75% of hyperactives, resulting in an overall correct classification rate of 82.5%. A caution is warranted in interpreting the findings of the discriminant function

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analyses. These tests were conducted using a sample which included 50% hyperactive children and 50% control children, as determined by the CTRS—R and CPRS—R. Therefore the discriminant functions produced were based on a prior probability that hyperactivity occurred 50% of the time. The base rate of preschool hyperactivity in the general population, as indicated by elevated scores on parent and teacher rating scales, is much lower; generally it is found in 14-20% of preschool boys and about 6% of preschool girls (Campbell, 1985). Thus the discriminant functions produced would need to be tested using a random sample of preschoolers from the general population to get a true judgement of their efficiency in identifying hyperactive and control children.

Discussion The purpose of this study was to assess the utility of a newly developed visual vigilance task, the Preschool Vigilance Task (PVT), in differentiating between hyperactive and control preschoolers, and to compare this measure to the well-established Continuous Performance Task (CPT). In addition, both measures were compared to a behavioral index of inattentiveness. The PVT is different from the CPT in that it was designed and tested exclusively for the preschool population. It does not require any knowledge of numbers or letters, a feature of the CPT which may penalize younger children. The PVT appears to be assessing the child's attentional ability in a relatively raw form, and does not demand as elaborate processing of information as tasks which require the recognition of numbers or letters. The PVT can be easily and quickly administered by non-professional personnel, thus offering a standard and objective measure of the child's attentional ability which can be used as an adjunetive aid in the evaluation of attentional deficits. Results are not affected by bias and unknown bases of comparison of the evaluator, factors which have been found to affect scores on behavioral rating scales typically used to assess hyperactive children (Schachar, Sandberg & Rutter, 1986). Both errors of omission and commission were found to be reliable measures on the CPT, while only errors of omission on the PVT demonstrated adequate reliability. Individual and group data on the PVT errors of commission were examined in an attempt to understand this measure's lack of reliability. This investigation revealed that there were three hyperactive subjects who committed extensive errors of commission on one session and not on the next, and that the overall data of the hyperactive sample were quite variable (mean = 76.00, S.D. = 175.85). This was not so with the control children. Given the rather impulsive and sporadic behavior characteristically exhibited by hyperactive children, especially those in the preschool years, this is not surprising. The nature of commission errors on the PVT is also different than for the CPT. When a commission error is committed on the PVT it is done so in the absence of the presentation of a new stimulus, whereas the CPT error is committed during the rapid presentation of non-target stimuli. Therefore children were responding reliably to the presence of irrelevant stimuli (CPT), but not to the absence of stimuli (PVT). The extended length of the PVT as compared to the CPT may be yet another contributing factor to the reliability discrepancy found with these two measures. These data may be an indication that errors of commission on the PVT cannot be used reliably

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to differentiate hyperactive and control preschoolers, but that high values on this measure are indicative of a potential problem with hyperactivity. Also the number of PVT errors of commission was significantly correlated with the behavioral index of inattentiveness (r= .89, p= .0001), lending further support to its probable utility. Hyperactive children in this study were found to commit more errors of commission and omission than control children on the CPT and more errors of omission on the PVT. These findings are consistent with previous studies implementing visual vigilance tasks with hyperactive school-age children (e.g. Doyle, Anderson & Halcomb (1976), Klee & Garfinkel (1983) and Sykes et al. (1973)). These children were not found to differ from their control counterparts in their reaction time on either task. Both errors of commission and omission on the CPT and errors of omission on the PVT were found to be related to the behavioral index of inattentiveness. This finding indicates that these measures were actually assessing inattentive behavior in preschool-age children and were not merely detecting some other factor that may have differentiated hyperactive from control children in our sample. Future directions and implications

The current study reveals that the PVT has potential as a useful adjunetive assessment/detection device for hyperactive preschoolers. A limitation of the reported findings is that since the CTRS—R and CPRS—R were the only measures used to ascertain group membership, the conclusions depend on the validity of these indicators of hyperactivity in preschool children. Before clinical usage can be advocated, more research must be conducted on the PVT. A need exists for large-scale studies to generate normative data for non-pathological and pathological children on this task. Such a standardization process should include investigations of the construct validity, concurrent validity and predictive validity of this newly developed measure. More extensive data on the reliability of the PVT are also needed. Acknowledgement—-This research was conducted as partial fulfillment for the first author's master's degree under the guidance of the second author. Portions of this work were presented at the annual Midwestern Psychological Association Conference, Chicago, May, 1990. The authors wish to thank Wendell Rohrer and Creg Kable for their computer programming assistance, and Sydney S. Zentall for her statistical and editorial assistance.

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Barkley, R. A. (1982). Guidelines for defining hyperactivity in children. In B. B. Lahey & A. E. Kazdin (Eds), Advances in clinical child psychology. Vol. 5, (pp. 137-180). New York: Plenum Press. Barkley, R. A. (1988). Attention deficit disorder with hyperactivity. In E. J. Mash & L. G. Terdal (Eds), Behavioural assessment of childhood disorders (2nd edn) (pp. 69-104). New York: Guilford Press. Campbell, S. B. (1985). Hyperactivity in preschoolers: correlates and prognostic implications. Clinical Psychology Review, 5, 405-428.

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Sykes, D. H., Douglas, V. L, Weiss, G. & Minde, K. K. (1971). Attention to hyperactive children and the effect of methylphenidate (Ritalin). Journal of Child Psychology and Psychiatry, 12, 129-139. Werry, J. S. & Aman, M. G. (1975). Methylphenidate and haloperidol in children. Archives of General Psychiatry, 32, 790-795. Werry, J. S. & Quay, H. C. (1969). Observing the classroom behavior of elementary school children. Exceptional Children, 2 5 , 461-470.

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The performance of hyperactive and control preschoolers on a new computerized measure of visual vigilance: the Preschool Vigilance Task.

This study examines the ability of a new visual vigilance task, the Preschool Vigilance Task (PVT), to differentiate between hyperactive and control p...
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